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Introduction to Field of View Overlay for WFIRST

The Barbara A. Mikulski Archive for Space Telescopes (MAST) contains infrastructure to overlay the locations and shapes of instrument apertures on images, and to perform spatial footprint queries on catalog databases. This has enabled the creation of a web service, which can be executed remotely to visualize the WFIRST Field of View (FOV), and to return catalog objects (e.g., GSC2, 2MASS, WISE) within specified detectors.

The interface allows one to specify a target name and lookup coordinates from SIMBAD (Set of Identifications, Measurements, and Bibliography for Astronomical Data) or the Extragalactic Database (NED) or to input a position directly. Once a telescope/instrument/aperture combination has been selected, then one can retrieve or display the footprint (Figure 1 below) as well as retrieve or display extractions from one of the catalogs (e.g., Figure 2 below). The portal defaults to displaying the DSS as the background sky image, however, SDSS and GALEX imagery are also available.

Known Limitations of the Prototype Tool

For the “Display Footprint” and “Display Catalog Data” functionalities to work, it may be necessary (e.g., in Safari or Chrome) to set your browser preferences to allow pop-up windows. This is not required by all browsers.

The display for the “Display Footprint” function defaults to a size of 0.2 degrees at the center of the telescope’s focal plane, rather than at the location of the aperture. The WFIRST Wide Field Instrument detectors have a significant offset from the center of the field of the telescope's focal plane (Figure 3 below), so the initial display will typically not show the aperture. Please zoom out and you will see the aperture at the offset location. If needed, you can drag the display location over to that point and zoom in again. The display for the “Display Catalog Data” function defaults to center on the first object in the retrieved catalog list. Here too, zooming out may be necessary to see all the catalog objects. Planned portal improvements will eventually allow specification of both the location and the size of sky display.

We cannot currently overlay both the aperture and the catalog on the same display because we can only instantiate the portal with one remote query at a time. Planned improvements to the portal API will eventually eliminate this restriction.